480 Journal of Agricultural Research voi. in. No. 6 



especially the generally higher results for the concentrates, indicate that 

 the direct stimulation of metabolism is a large factor. 



It appears, then, that while the mechanical work required for the 

 dio-estion of concentrates is somewhat less than that necessary in case 

 of coarse fodders, this difference is more than compensated for by other 

 factors, so that on the whole fully as great an increase in the heat pro- 

 duction is caused by the consumption of the concentrates. As a class, 

 concentrates are superior to coarse fodders, not because their consump- 

 tion involves a less expenditure of energy, but because they contain 

 more metabolizable energy, so that more remains available for body use 

 after that expenditure has been met. 



DIFFERENCES BETWEEN FEEDING STUFFS 



But while our results do not show the existence of as great differences 

 between the two great classes of feeding stuffs in their effects on the 

 energy expenditure of the body as seems to have been at times assumed, 

 they nevertheless reveal distinct differences even between feeding stuffs 

 of the same class. Thus, among the hays (if the results of experiment 

 179 for clover hay are accepted) a regular increase is found in the total 

 energy expenditure from timothy hay with an average of 782 Calories 

 through mixed hay and clover hay up to alfalfa with an average of 

 1,169 Calories. Apparently the legumes cause a distinctly greater 

 increase in the metabolism than the Poaceae (Gramineae). In the case 

 of red clover, the difference, according to the meager results obtained, 

 appears to result chiefly from a stimulation of the metabolism due to 

 standing. With alfalfa, on the contrary, the increase in the standing 

 metabolism is not materially greater than in the case of timothy hay, 

 while that due to fermentation is somewhat less. The chief difference 

 between the two seems to He either in their effect upon the work of 

 peristalsis or in the degree to which they stimulate the general metab- 

 olism. One can hardly doubt that the latter is the chief cause and is 

 naturally inclined to associate it with the higher percentage of protein 

 in the legumes. That other causes may also be operative, however, is 

 indicated by the result on maize stover, which is nearly as high as in the 

 case of alfalfa and shows a similar distribution among the several factors. 



Among the concentrates there may be noted particularly the marked 

 effect of maize in both the two not very satisfactory experiments in 

 noticeably increasing the standing metabolism. This result is of special 

 interest in view of Zuntz and Hagemann's observations (52, p. 259) on 

 the stimulating effect of maize upon the metabolism of the horse, which 

 were also made on the standing animal, although no increase in the 

 minor muscular activity is reported. Grain mixture No. i, containing 

 43 per cent of maize meal, likewise showed a similar effect, although 

 with grain mixture No. 2, containing 60 per cent of maize, it was much 

 less marked, possibly on account of the lower content of protein (12.5 

 as compared with 17.5 per cent). The increases caused by wheat bran 



